• Journal of Biosystems Engineering
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• 제35권3호
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• pp.182-188
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• 2010

Post-Harvest processing engineering is a field that studies prevention of the quality change of agricultural products during sorting, packaging, storage, and distribution after harvested. In distribution steps, agricultural products could be damaged by physical force, it is the main reason of low quality and they lost value of commodities. This study was performed to find the vibration characteristics of the peach, and to find the extent of the damage on the peach by fatigue stress. The vibration data was obtained on expressway and the vibration characteristics of peach was used to find the damage on the peach. To analyze the vibration characteristics of peach, the resonance frequency and vibration transmissibility were measured. The resonance frequency of the peach was 167.98 Hz and the transmissibility was 4.06 at resonance point. It was 150 ~ 250 Hz that the transmissibility was more than 1. And the transmissibility in simulated test was measured. When the trasmissibility was more than 1, the range was 15 ~ 65 Hz, and when it was less than 1, the range was 65 ~ 175 Hz. When the transmissibility was about 1, the range was 5 ~ 15 Hz. The damage and the vibration cycle numbers of peaches were compared with input frequency and acceleration. More damage and less cycle number happened in 30 Hz than in 62.5 Hz. The reason was that the transmissibility of 30 Hz was higher and the vibration displacement in lower frequency was more. The more acceleration and cycle number increased, the more the bruising volume of peaches increased. The bruising volume ratio for vibration fatigue was measured according to input acceleration and cycle number. Using measured data, regression models for bruising volume ratio(BVR) was developed as a function of the acceleration(A) and cycle number(CN) as follows. BVR = a * $A^b*$ $(CN)^c$

• 천문학회보
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• 제39권1호
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• pp.84.1-84.1
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• 2014

We report the spatial distribution of early-type stars and pre-main-sequence (PMS) stars around the starburst type young open cluster Westerlund 2. The early-type were selected from UBVI photometric data, while the PMS members were identified from their X-ray emission and mid-infrared excess. The northern clump of the cluster is composed mainly of PMS stars detected in both optical and X-ray and seems to be coeval to the cluster, while PMS stars in the bright bridge region are highly obscured in optical wavelength. The bright bridge appear to be an on-going star forming region possibly triggered by the strong radiation field from both sides-massive stars in Westerlund 2 and WR 20b. We also found that there are many early-type stars not only in the cluster but also farther from the cluster up to several times of the cluster radius. These early-type stars are well aligned from east to southwest of the cluster. We conclude these early-type stars are members of an OB association in the RCW 49 nebula. This report indicates there is a complex star formation history in Westerlund 2 and its surrounding H II region, the RCW 49 nebula.

• 한국전자파학회논문지
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• 제11권6호
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• pp.976-983
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• 2000

본 논문은 MRI용 RF 코일로 널리 사용되고 있는 Birdcage type의 RF 코일을 FDTD 방법을 이용해서 해석, 설계하였다. 기존의 저자장(1T, 1.5T) MRI용 RF 코일의 해석 방법은 코일의 공진 주파수를 얻기 위해서 LC 등가 회로를 사용하였으며 코일 내부의 필드 분포를 얻기 위하여 Biot-Savart 법칙을 이용한 방법이 널리 사용되어 왔다. 그러나 3T이상의 고주파에서 동작하는 RF 코일의 해석에는 위의 방법이 커다란 오차를 일으킬 수 있다. 따라서 본 논문에서는 고주파 해석이 가능한 전파 (Full Wave) 해석 방법인 FDTD 방법을 이용하여 3T MRI용 RF 코일을 해석하고 설계하였다. 또한 FDTD 방법을 이용하여 본 논문에서 실제 제작된 Birdcage type과 Spiral type RF 코일에 적용하여 이 방법의 타당성을 실험적으로 검증하였으며 Spiral type의 RF 코일이 B1 field 균일도면에서 Highpass Birdcage type보다 우수함을 수치 해석적으로 검증하였다.

• 한국토양비료학회지
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• 제50권5호
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• pp.422-433
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• 2017

Unmanned Aerial Vehicle (UAV) has several advantages over conventional remote sensing techniques. They can acquire high-resolution images quickly and repeatedly. And with a comparatively lower flight altitude, they can obtain good quality images even in cloudy weather. In this paper, we developed for estimating garlic growth at field scale model in major cultivation regions. We used the $NDVI_{UAV}$ that reflects the crop conditions, and seven meteorological elements for 3 major cultivation regions from 2015 to 2017. For this study, UAV imagery was taken at Taean, Changnyeong, and Hapcheon regions nine times from early February to late June during the garlic growing season. Four plant growth parameters, plant height (P.H.), leaf number (L.N.), plant diameter (P.D.), and fresh weight (F.W.) were measured for twenty plants per plot for each field campaign. The multiple linear regression models were suggested by using backward elimination and stepwise selection in the extraction of independent variables. As a result, model of cold type explain 82.1%, 65.9%, 64.5%, and 61.7% of the P.H., F.W., L.N., P.D. with a root mean square error (RMSE) of 7.98 cm, 5.91 g, 1.05, and 3.43 cm. Especially, model of warm type explain 92.9%, 88.6%, 62.8%, 54.6% of the P.H., P.D., L.N., F.W. with a root mean square error (RMSE) of 16.41 cm, 9.08 cm, 1.12, 19.51 g. The spatial distribution map of garlic growth was in strong agreement with the field measurements in terms of field variation and relative numerical values when $NDVI_{UAV}$ was applied to multiple linear regression models. These results will also be useful for determining the UAV multi-spectral imagery necessary to estimate growth parameters of garlic.

• 대한치과기공학회지
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• 제25권1호
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• pp.41-62
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• 2003

In this research, we manufactured the paste opaque porcelains using Propylene Glycol (PG) and Buthylene Glycol (BG) as a solvent, and compared the composition of solvents, the coefficient of thermal expansion, the particle size distribution, the viscosity and bonding strength to metal, and the tone with those of the commercial products(Duceram Plus, Duceram GmbH; VMK 95, Vita Co.; Noritake EX-3, Noritake Co.)used in the clinical field. The results of the research were as follows: 1. The result of solvent analysis indicated that the solvents included in the paste opaque porcelains of the control group were mainly composed of Glycols. 2. From the Coefficient of thermal expansion measurement, we drew out the following results; testing group: $14.0\times10^{-6}/^{\circ}C$, Duceram Plus: $13.9\times10^{-6}/^{\circ}C$, VMK 95: $14.3\times10^{-6}/^{\circ}C$, and Noritake EX-3: $13.3\times10^{-6}/^{\circ}C$. 3. Seen from the result of particle size distribution measurement, the experimental group was similar to the control group in 1$\mu m$ below, but the experimental group marked the highest distribution of 61% in the case of between 1$\mu m$ and 5$\mu m$. Between 5$\mu m$ and 10$\mu m$, they showed relatively similar distribution, and Noritake EX-3 was turned out the highest distribution of 29% in 10$\mu m$ above. 4. From the result of viscosity measurement, Duceram plus showed the highest viscosity throughout all the measurements followed by Noritake Ex-3, experimental group and VMK 95 in decreasing order. 5. The result of bonding strength measurement was EX 35.53 $\beta\acute{A}$, DU 40.88 $\beta\acute{A}$, VM 39.43 $\beta\acute{A}$, and NO 35.39 $\beta\acute{A}$, and no significant difference was found between the experimental group and the control groups(P>0.05). 6. The measurement of the tone indicated that the $L^*$ value of the experimental group was 86.89 0.63 in average, which is higher than the control group in its brightness. In the case of the $a^*$ value, Duceram Plus, VMK 95 and EX-3 showed positive value, whereas the testing group was turned out negative value. In $b^*$ value, Duceram Plus proved the highest. From the results of this research, the paste opaque porcelains using Propylene Glycol (PG) and Buthylene Glycol (BG) as a solvent did not make differences from the commercial products that are actually used in the clinical fields. Therefore, it is possible to utilize Propylene Glycol (PG) and Buthylene Glycol (BG) for the paste opaque porcelains of P.F.M crown. It is also recommended that further researches concerning the compositions and forms of powder, the types of organic solvent components and the ratio of mixture proceeded in order to improve the level of productivity in the future.

• Progress in Superconductivity
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• 제10권1호
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• pp.60-67
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• 2008

We present domestic efforts for superconducting fault current limiter (SFCL) application in the Korea Electric Power Corporation (KEPCO) grid and pending points at issue. KEPCO's decision to upgrade the 154 kV/22.9 kV main transformer from 60 MVA to 100 MVA cast a problem of high fault current in the 22.9 kV distribution lines. The grid planners supported adopting an SFCL to control the fault current. This environment friendly to SFCL application must be highly dependent upon the successful development of SFCL having specifications that domestic utility required. The required conditions are (1) small size of not greater than twice of 22.9 kV gas insulated switch-gear (GIS), (2) sustainability of current limitation without the line breaking by circuit breakers (CB) for maximum 1.5 seconds. Also, optionally, recommended is (3) the reclosing capability. Conventional resistive SFCLs do not meet (1) $\sim$ (3) all together. A hybrid SFCL is an excellent solution to meet the conditions. The hybrid SFCL consists of HTS SFCL components for fault detection and line commutation, a fast switch (FS) to break the primary path, and a limiter. This characteristic structure not only enables excellent current limiting performances and the reclosing capability, but also allows drastic reduction of HTS volume and small size of the cryostat, resulting in economic feasibility and compactness of the equipment. External current limiter also enables long term limitation since it is far less sensitive to heat generation than HTS. Semi-active operation is another advantage of the hybrid structure. We will discuss more pending points at issues such as maintenance-free long term operation, small size to accommodate the in-house substation, passive and active control, back-up plans, diagnosis, and so on.

• 한국자기학회지
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• 제16권1호
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• pp.14-17
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• 2006

졸겔법을 이용하여 $AIFeO_3$ 단일상을 제조하였으며, 그 결정학적 및 자기적 특성을 X선 회절법(XRD), 진동 시료 자화율 측정법(VSM), 뫼스바우어 분광법으로 연구하였다. 결정구조는 공간군이 $Pna2_1$ orthorhombic 구조로 분석되었으며, 격자 상수는 각각 $a_0=4.983\;{\AA},\;b_0=8.554\;{\AA},\;c_0=9.239\;{\AA}$임을 알 수 있었다. VSM을 이용하여 65K에서부터 상온까지 여러 온도 구간에서 자기이력곡선을 측정하였으며, 강자성 특성과 함께 저온영역에서 자기 이력 곡선의 비대칭성이 관측되었다. 온도에 따른 자기모멘트 측정 결과로부터 자기전이온도는 250k로 결정하였다. 뫼스바우어 스펙트럼은 4.2K에서부터 상온까지의 온도 영역에서 측정하였으며, 분석 결과 상온에서 이성질체 이동치는 0.32mm/s로 철의 이온상태가 ferric임을 확인할 수 있었다. 온도변화에 따라 측정된 뫼스바우어 스펙트럼 분석은 온도에 따라 선폭이 증가함이 관측되었는데, 이러한 흡수선의 비대칭적 선폭 증가는 1개의 사면체자리와 3개의 팔면체 자리의 Fe이온 분포와 각 부격자간 자기이방성 에너지 차이에 따른 결과로 해석된다.

• 한국작물학회지
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• 제52권2호
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• pp.220-227
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• 2007

Sweetpotato fields in Korea are highly infected with virus and virus like diseases that greatly diminish both yield and quality as indicated by field observations and laboratory tests. In order to solve this problem, there is an urgent need to produce and mass propagate virus-free planting materials for distribution to the farmers. These experiments were conducted, firstly, to determine the most appropriate culture media, nutrient solution, and cutting intervals to maintain growth and vigor of tissue cultured plantleta as mother plants for propagation in insect-proof greenhouse. And as a labor saving method, the production efficiency of plug trays for rapid propagation of stem cuttings as a source of planting materials was likewise evaluated. Results showed that plants grown in medium B supplied with 0.5 and 1.0 strength of MS nutrients had high growth rate, and 20-day cutting interval was the best. 72-plug tray was better than 128-plug. Secondly, it was to develop a technique for the production of first-generation seed roots using hydroponics cultivation system. The yield of virus-free plants propagated in the non-insect proof and open-field cultivation was 2,402 kg/10a, 6% higher than those in the insect-proof cultivation, and the rate of virus re-infection was 18% higher compared to 3.3% with insect-proof cultivation. Lastly, it was to investigate the growth performance of virus free plants in farmers' field. Differences were existed in the yield depending on the variety used, but virus free plants showed an increase of $6{\sim}24%$ over virus infected plants.

• 한국자기학회지
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• 제3권3호
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• pp.179-184
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• 1993

비정질 합금 $Fe_{78}Si_{9}B_{13}$의 구조를 X-선 회절상을 분석하여 구하였다. 계산된 동경분포함수(RDF)의 첫번째 peak는 최인접 원자의 분포를 나타내는 것으로 Gaussian 함수형태를 나타낸다. 구조분석에서 본 시료의 최인접 원자배위수는 13.5이고, 최인접 원자간 평균거리 $r_{0}$는 $2.595{\AA}$, 인접원자들의 분포를 나타내는 Gaussian 함수의 변수 ${\delta}r$은 $0.27{\AA}$이다. 저온에서의 포화자화의 온도 의존성은 spin 파로 설명할 수 있으며, 이 때에 계산된 spin파 stiffness 상수는 $117.8\;meV\;{\AA}^2$ 이다. 또한, 포화자화의 온도 의존성을 Handrich의 분자장 이론식과 맞추어 얻은 변수는 각각 S=1/2 일때 ${\Delta}=0.32$이고, S=1 일때 ${\Delta}=0.23$으로 이론식과 실험결과가 전체적으로 잘 일치한다. 구조분석 결과와 분자장 이론식에서 구한 변수를 활용하여 spin파 stiffness 상수를 계산할 수 있으며, 이로써 구한 값은 S=1/2일때 $149\;meV\;{\AA}^2$ 이고, S=1 일 때 $138\;meV\;{\AA}^2$ 이다. 또한, 평균 교환결합상수 J($r_{0}$)는 S=1/2일때 17.9 meV이고, S=1일때는 J($r_{0}$)는 6.7 meV 으로 추정된다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.234.1-234.1
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• 2014

Many studies have been investigated on high density plasma source (Electron Cyclotron Resonance[ECR], Inductively Coupled Plasma[ICP], Helicon plasma) for large area source after It is announced that productivity of plasma process depends on plasma density. Among them, Some researchers have been studied on multiple sources In this study, we attempted to determine the possibility of multiple inductively coupled plasma (ICP), and helicon plasma sources for large-area processes. Experiments were performed with the one and two coils to measure plasma and electrical parameters, and a circuit simulation was performed to measure the current at each coil in the 2-coil experiment. Based on the result, we could determine the possibility of multiple ICP sources due to a direct change of impedance due to current and saturation of impedance due to the skin-depth effect. However, a helicon plasma source is difficult to adapt to the multiple sources due to the consistent change of real impedance due to mode transition and the low uniformity of the B-field confinement. As a result, it is expected that ICP can be adapted to multiple source for large-area processes.